On the other hand, the merger of equal mass, nonspinning BBH systems are expected to result in a remnant BH with \(a \sim 0.7\) . As a result, population simulations predict that hierarchical mergers resulting from products of nonspinning first-generation mergers will leave a signature of a subpopulation of BH spins peaked around \(a \sim 0.7\)  with tails extending from \(a \sim 0.5\)  to \(\sim 0.9\)  [1]}. Referring back to Figure REF , we do not see evidence of an obvious subpopulation in this high-spin region of interest, but rather some preference for low-spin magnitudes, possibly indicating that hierarchical mergers are not providing the dominant formation mechanism for the observed BBHs. The lack of support for a relatively high spin subpopulation is consistent with the conclusions drawn in [2]}, [3]}. Assuming that BBHs from hierarchical mergers all have \(a>0.5\) , we infer that no more than \({23\%}^{+14\%}_{-11\%}\)  of the astrophysical population of merging BBHs form through a hierarchical merger channel.
